1. Field of the Invention
The present invention relates to a reactor with hydrogen adsorption alloy composed mainly of metal hydride, and, more particularly, to a novel construction of the reactor whose heat exchanger effectiveness is considerably improved as compared with the prior art.
2. Prior art
Heretofore, in several fields apparatus have been developed in which hydrogen is adsorped in a certain metal or alloy to be stored therein and transferred therefrom in the form of a metal hydride, and those apparatuses have been further applied to such practical use as purification of hydrogen, pressure rise, heat pump, air-conditioning system, etc.
In such case, because an exothermic reaction or endothermic reaction necessarily takes place at the time the metal hydride adsorbs or discharges hydrogen, it is possible to take advantage of such a property for a heat exchanger, heat pump, etc.
When it is a principal object to store and transfer hydrogen, delivery of hydrogen is not effectively carried out without rapid delivery of heat between the metal hydride and the outside in view of the high thermal efficiency of the heat exchanger, or efficient storage and transfer of hydrogen.
However, thermal conductivity of hydrogen adsorption alloy itself in the form of particles is not high, and therefore several attempts have been proposed aiming at efficient delivery of heat.
According to one of such proposed attempt, in order to improve the hydrogen adsorption alloy itself, surfaces of the particles are plated with a different kind of metal of high thermal conductivity as described later. The applicant of the present invention has already proposed an attempt as is disclosed in Japanese Patent Application No. 59-46161, entitled "Method for Producing Hydrogen Adsorption Alloy". There have also been proposed several attempts to solve the problem by the manner in which the heat exchanging reactor as constructed including the attempt disclosed in the Japanese Laid-Open Utility Model Publication (unexamined) No. 61-193300 (see FIG. 3), entitled "Hydrogen Adsorption Alloy Storage Tank". According to the device disclosed in this laid-open application, a tank is formed of multiple concentric pipes, in which a passage area of heating or cooling medium and a charging area of hydrogen adsorption alloy are alternately located, and the thickness of the alloy charging layer is specified.
A further attempt has been proposed in which hydrogen adsorption alloy is not used in the form of particles but is stored in a tank in the form of a compressively formed compact, as is disclosed in U.S. Pat. No. 4,717,629 (see FIG. 4), Japanese Laid-Open Patent Publication (unexamined) No. 62-196500) entitled "Heat Exchanging Unit with Hydrogen Adsorption Alloy", in addition to the above-mentioned Japanese Patent Application No. 59-46161. It may be said that any of these proposals succeeds in overcoming such drawbacks as low thermal conductivity of the alloy particle charged layer itself, deterioration of such conductivity by decay and micronization of the alloy due to repetition of reaction with hydrogen gas.
The aforementioned prior art, however, still have the following disadvantages or problems to be solved.
When hydrogen gas passes through the layer of hydrogen adsorption alloy in the form of particles, there arises a problem of micronization and dispersion of the particles, which seems to restrict the effectiveness of the hydrogen adsorption alloy, which restriction cannot be overcome by a simple variation or modification of construction of the heat exchanger tank alone. In the prior art shown in FIG. 3, because expansion of the alloy and/or micronization thereof take place increasingly, the bottom part of the alloy becomes condensed and solidified thereby bringing about excessive deformation of the tank, which eventually results in breakdown of the reactor.
In any of the proposals according to which fine compacts are prepared and incorporated in the heat exchanger tank, because the heat exchanger accommodating the compacts still follows the traditional heat exchanger design which does not use hydrogen adsorption alloy, transfer of the heating or cooling medium is so slow that satisfactory improvement in heat exchanger effectiveness cannot be attanined. Moreover, because of the large residence time in the tank, it takes a lot of time in the operation of adsorption (cooling) and discharge (heating) of hydrogen gas and in the switching operation therebetween.